The present invention relates to a process for manufacturing a thyristor in a semiconductor body, which contains an area which has a lower breakdown voltage than the rest of the semiconductor body, and it relates, more particularly to a thyristor whose semiconductor body has at least a first major surface containing a control electrode, a second major surface and a first base region with an adjacent second base region.
These types of processes are known, for example, from German Patent document No. DE-OS 23 00 754 and serve to permit a controllable breakover firing of the thyristor in this area at the predetermined lower breakdown voltage. In that document, the area which has a lower breakdown voltage than the rest of the semiconductor body of the thyristor is manufactured, for example, by making the second base region thinner in this area than it is outside this area.
In German patent document No. DE-OS 23 46 205, a method is disclosed for forming the area with the lower breakthrough voltage in the semiconductor body by specially selecting as starting materials for the semiconductor body semiconductor disks which have a clearly defined area with a lower specific resistance. Semiconductor disks of this kind can be manufactured, for example, by a special silicon drawing process.
Another possibility for forming an area at the edge of the semiconductor body which has a lower breakdown voltage than the rest of the semiconductor body might consist in making the edge profile of the semiconductor body with a negative angle.
These familiar processes have the disadvantage that they often provide an unsatisfactory yield.